1. Field of the Invention
The invention relates generally to exercise equipment, and more particularly to a treadmill for exercising the upper and lower body of a user. More specifically, the present invention relates to a motorless treadmill powered by arm members that move at rates independent of each other.
2. Prior Art
Treadmills for providing a striding or walking exercise surface are well known in the art. Conventional treadmills employ a motor to rearwardly drive an endless belt as a user maintains a striding motion on the exercise surface. Generally, the user of a conventional treadmill is able to vary the speed and incline of the treadmill to obtain a desired level of workout. More sophisticated treadmills, such as described in U.S. Pat. No. 5,462,504 and assigned to the assignee of the present application, automatically adjust the speed and incline of the treadmill to control the heart rate of the user during exercise.
In general, treadmills function to exercise the user's cardiovascular system and the skeletal muscles of the lower body, but do not exercise the upper body to any significant extent. Accordingly, a number of treadmills have an upper body exercise means, such as upstanding arm members, which are moveable by the user against the resistance of a spring or friction brake.
While conventional motor-driven treadmills provide a desirable exercise apparatus in appropriate settings, in other settings the motor makes such an apparatus undesirable. For example, motors used in treadmills need maintenance, can fail, require a power source and add to the overall weight of the treadmill. Finally, motor-driven treadmills are more expensive to purchase relative to motorless treadmills. As a result, manual treadmills are known in the art which do not use motors, but instead are designed to be inclined such that the belt rotates rearwardly as a result of the weight and forward striding action of the user overcoming belt friction. In these types of treadmills it is important for the treadmill surface to maintain a certain minimum level of incline to power the belt rearwardly by the weight of the user exerting a force downward upon the inclined plane of the treadmill. However, such a steep incline of the treadmill surface feels unnatural to the user, and is not at all like the user's normal walking motion.
More sophisticated manual treadmills, such as the manual treadmill described in U.S. Pat. No. 5,688,209 and assigned to the assignee to the present application, use the motion of the user's arms through movement of arm members linked to the treadmill to power the belt in a rearward direction. However, the right arm member of the treadmill disclosed in the patent is reciprocally linked to the left arm member requiring both arm members to move at the same rate to provide the desired rearward movement of the belt. Only moving a single arm member in either the forward or rearward direction will cause the belt to move rearwardly. However, due to the interlinked relationship of the arm members, both arm members must move at the same rate and in the opposite directions of one another, which may not be the preference of the user. Therefore, there exists a need in the art for a manual treadmill that includes arm members that power the belt at rates independent of each other such that operation of one arm member in either reciprocating direction powers the belt.